The present invention is related to application Ser. No. 11/834,752, filed Aug. 7, 2007, now U.S. Pat. No. 7,854,547 and entitled “Bidirectional and Expandable Heat Flow Measurement Tool for Units of Air Cooled Electrical Equipment” which is directed to ascertaining conditions related to individual electronic components, such as servers. The measurement tool illustrated and described is mounted sequentially at the front and then at the back of the device under test to obtain air pressure and temperature values, which in turn enable the air flow and rate of heat dissipation to be determined. This measurement tool also presents a marginal surface, which engages the device, that is compliant to allow any cables to remain connected to the device and continue device operation during test.
At the rack level it is also necessary to obtain data regarding physical conditions to assist installation and determine whether subsequent operating conditions comply with the design requirements. The problems encountered by the assembly of numerous devices at the rack level differs from those for an individual device and requires different solutions.
As individual electronic components are improved, the power consumption is usually reduced; however, since the concentration of components is rapidly increased, the concentration of power and the requirement to dissipate heat from a given space is increased. The number of components concentrated in a given space rises faster than the power requirements diminish. Adequate heat sink capability and air flow capacity must be increased commensurate with the increase in power. To assure adequate heat dissipation, water cooling is also employed to assist heat dissipation. The use of water cooling also introduces a further level of concern when employed with electronic equipment.
To comply with data center owner's preferences or outright requirements, it is necessary that any equipment or system test be effected non-invasively and be non-disruptive with respect to operating equipment. No customer or user is likely to allow equipment to be turned off to obtain information such as an inline power measurement. In the rack mount environment, it is also necessary that the heat dissipation capability be determined with rack covers in place so that this second order effect is included in the determination of the effectiveness of the overall system. Similarly, the equipment utilized for testing must be designed and used in a manner that imposes minimal additional effect on the system subject to investigation.
In a rack mount enclosure it has been found that a vertical temperature gradient through the height of the rack enclosure air input opening must be accommodated to obtain an accurate determination of localized heat dissipation in addition to overall air flow and heat dissipation values. The temperature must be observed at multiple vertically spaced locations calculated to accurately represent the variation of temperature over the height of the enclosure opening. It is also preferable practice to obtain sensed values, such as temperature simultaneously at both the inlet and outlet locations of the system.
At the outlet of the cabinet, the air flow may be collected and routed through a single duct for sensing air pressure and temperature (to obtain respectively a calculated air flow and temperature difference). Such an approach materially adds to the air pressure drop of the system and results in undesirable vector effects at the exit caused by a large volume of air being turned 90 degrees approaching the single outlet. Air resistance can be reduced to obtain a more accurate and representative value of air flow and mean air temperature, while accommodating the vertical temperature gradient, by employing multiple exit ducts vertically spaced through the height of the rack enclosure outlet opening. The outlet air flow is further stabilized by the use of horizontal flow partitioners between adjoining exit ducts. The measurement of the quantity of heat removed from the enclosure can be made with greater accuracy by also determining the relative humidity at the locations at which temperature is determined to obtain the specific heat in the air volume passing through the enclosure.
When used with a rack enclosure assembly that includes water cooling, the relative humidity sensed at the locations at which the temperature is determined can also provide a determination of the absolute humidity entering and leaving the enclosure. A rise of absolute humidity between the rack enclosure inlet and outlet air openings can be used to initiate a signal calling for a check of the integrity the water cooling system.
In the environment wherein enclosures are used to house units of identical blower or fan cooled devices, the use of known device fan or blower rotational speeds (RPM) can be utilized in the calculation of rack enclosure air flow and heat dissipation values.